The ancient Greeks believed their gods lived on Mount Olympus and included Zeus, Poseidon, Hades, Athena, Aphrodite, Apollo, and Hephaestus. Zeus was the all-powerful king of the gods who used lightning bolts. Poseidon was god of the sea who could unleash storms and sailors prayed to him for safe voyages. Hades ruled the underworld where the dead lived as ghosts.